From: The role of motion capture in an illusory transformation of optic flow fields Journal of Vision. 2008;8(4):27. doi:10.1167/8.4.27 Figure Legend: Target flow speed dependence of the horizontal (○) and vertical (◊) focus shifts in the rotary OFI (a) and the radial OFI (b) in three participants (rows). The horizontal axes represent the speed of the target flow, expressed in spin rate (Hz) for the rotary flow, and simulated translation speed (m/s) in the radial flow conditions. Positive horizontal shift values indicate shifts in the direction of the inducer. Positive vertical shift values indicate shifts at an angle of 90° in the counterclockwise direction with respect to the inducer direction. Each shift is collected with inducer speeds of 5, 0, and −5°/s. In the rotary OFI (a), horizontal inducer motion caused vertical shifts (◊) in all subjects. These shifts were positive in clockwise flow and negative in counterclockwise flow. Significant horizontal shifts (○) were also observed in all participants. Both the vertical and the horizontal shifts were greatest at low target flow speeds. This comes to expression also in bar graph (c), which shows the parameters obtained by fitting Equation 2 to the vertical shifts and Equation 3 to the horizontal shifts. The parameters b y and b x from the spin rate R term are significantly non-zero in all three subjects, whereas the offsets a y and a x are significantly non-zero in only one case. This indicates that both horizontal and vertical shifts in the rotary OFI depend on target flow speed. In the radial OFI (b), the indicated focus positions of expanding and contracting flow were not biased in the vertical direction (◊). Horizontal shifts, however, did occur (○). Here too, shifts were largest at low target flow speeds. Offset c x is significantly non-zero in all participants (d), meaning that the horizontal shift of the FOE was larger than the shift of the FOC. The dashed line in panel b fitted to the horizontal radial focus shifts is the sum of Equations 2 and 3 that were fitted to rotary flow shifts in panel a, see Appendix A for details. Bars per parameter in panels c and d correspond from left to right to participants in panels a and b from top to bottom. All error bars are 95% confidence intervals. The filled black markers correspond to the data in Figure 3. Date of download: 11/13/2017 The Association for Research in Vision and Ophthalmology Copyright © 2017. All rights reserved.